Method and Apparatus for Synchronizing Clocks Underwater Using Light and Sound

摘要

Methods and systems for synchronizing clocks used in underwater devices is described. All clocks have some drift due to frequency accuracy and this disclosure provides a method for periodically synchronizing clocks to an accurate master clock to remove long term drift. A synchronization device can use an accurate clock and hardware to transmit both a sound wave and light pulse at the same point in time. Remote slave clocks can detect the light first, and later the sound, allowing them to calculate the distance the pulse had to travel. The clocks can then synchronize their time to the master clock canceling out any drift. The synchronization device can be packaged in a waterproof housing and can be moved around on a periodic basis between the clock on an underwater robot or any other means.

主权项

1. A method for synchronizing underwater slave clock devices from a master clock device wirelessly, comprising:
transmitting from the master clock device a light pulse and a sound pulse; receiving at a slave clock device the light pulse and the sound pulse; calculating at the slave clock device, based upon the difference in arrival times of the light pulse and the sound pulse, a distance between the master clock device and the slave clock device; calculating at the slave clock device, based upon the distance between the master clock device and the slave clock device, the time at which the light pulse was transmitted from the master clock device; applying at the slave clock device a time offset to a clock on the slave clock device based upon a difference between the time that the light pulse was transmitted according to a clock on the master clock device and the calculated light pulse transmission time calculated at the slave clock device.